From bone to heart: a case of MRSA osteomyelitis with haematogenous spread to the pericardium

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a pervasive organism that causes life-threatening illnesses. 1 Although there are many cases of skin and soft tissue infections secondary to MRSA, there are only five described cases of purulent pericarditis due to MRSA, and these are in the paediatric literature. 2 3 Purulent pericarditis is an accumulation of purulent fluid within the pericardial space. 4 We describe a case of refractory septic shock with pericardial involvement, resulting from MRSA osteomyelitis.

Case presentation

A 55-year-old woman was brought to the emergency department after a syncopal episode. Her medical history was significant for type 2 diabetes mellitus, end-stage renal disease requiring maintenance haemodialysis and Charcot arthropathy. Three months prior to the current admission, she was treated for MRSA bactaeremia from an unknown source, with an 8-week course of intravenous daptomycin.

During the index admission, the patient was brought to the emergency room, with syncope. On further evaluation, she was noted to have a temperature of 96.4°F, heart rate of 122 bpm and blood pressure of 96/61 mm Hg. Physical examination was significant for muffled heart sounds and diffuse crackles in bilateral lung fields. She also had local signs of inflammation, including swelling, redness, warmth and tenderness in her right lower extremity, however, she had no signs of inflammation at the site of her arteriovenous (AV) fistula. Thus, the most likely source of infection was the right lower extremity rather than the AV fistula. She was given intravenous fluids and started on antibiotics. She was then transferred to the intensive care unit, for a higher level of care.

Investigations

Blood tests revealed white cell count of 25.1x10⁹ /L (normal value 3.4-10.4x10⁹ /L) and C reactive protein of 279.2 mg/L (normal value 0.2-5 mg/L).

An initial diagnosis of septic shock due to an infective focus in the right foot was made. The patient was started on vancomycin, linezolid and ceftaroline for the MRSA coverage, given the prior history of MRSA bacteraemia. She was adequately fluid resuscitated and started on norepinephrine, however, she continued to be in refractory shock.

A bedside echocardiogram was performed at this time, showing a large pericardial effusion. A detailed transthoracic echocardiogram performed later showed a moderate-sized pericardial effusion with pericardial fibrinous stranding but no evidence of...